In digital camera applications, white balance can be an important process. White balance is typically used to correct for image sensor responses in order to better match an image with a user's perceptual experience of the object being imaged. The human eye can easily identify gray objects in all lighting conditions and interpret them as gray. For some imaging sensors, however, a white balance process is typically needed to make gray objects appear gray in the processed images.
There are multiple ways to perform automatic white balancing. The most commonly used approach is based on an assumption referred to as the “gray world assumption.” The gray world assumption postulates that, for a picture that contains multiple colors, the average of all these colors will turn out to be gray.
The white balance process is typically dependent upon the lighting condition associated with an image. Thus, in order to accurately perform a white balance process on an image, it is necessary to determine the lighting condition associated with that image. Different lighting can cause gray pixels to be defined differently within a given color space.